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rabblerouzer writes "Antiforensic tools have slid down the technical food chain, from Unix to Windows, from something only elite users could master to something nontechnical users can operate. 'Five years ago, you could count on one hand the number of people who could do a lot of these things,' says one investigator. 'Now it's hobby level.' Take, for example, TimeStomp. Forensic investigators poring over compromised systems where Timestomp was used often find files that were created 10 years from now, accessed two years ago and never modified."

Imagine a filesystem that is encrypted 3 times, in "headerless" fashion. What I mean by headerless is, whereas a zip file leaves reliable signatures identifying it as a zip file, this scheme would be a naked 128 or 256 or 1024 bit encrypted file (bear with me here) with no signature. There would be no way to even identify this file unless you managed to decrypt it with the right password and the exact corresponding decryption scheme. (It could be a zip file or a rar file or an arj file but you'd have to guess.)

That's for the first layer. Then you use the same (or different) scheme to scramble that already encrypted file again. With the same or different password.

Then you do it a third time.

Granted this would take a hell of a lot of computing power and a single bit of data corruption would screw you royally (which calls for more advanced recovery techniques which leads to some weaknesses...), but the effect is this.

First, you get the hard drive and the whole filesystem is encrypted. It's utterly garbage to you. You don't know which scheme was used to encrypt it. You certainly don't know the password. But you may know it's triple layer encrypted. Or double, or quad.

What is certain is, if you get the correct encryption scheme AND the password for that first layer, the decrypted file is STILL GARBAGE. You don't really know if you got the correct information or not, because you're still looking at a "headerless" pile of garbage data. Good luck guessing that second layer because no matter what, you still get a pile of incoherent garbage.

If you've done this to all your files on your hard drives, DVDs and CDs, this is where you demand your Constitutional right (in the United States) to a SPEEDY trial and then plead the Fifth Amendment in court when asked for your password/encryption schemes. Why? Because if I'm right, the police and their descendants down to the 7th generation will have died of old age before they figure out the 2nd layer, much less the 3rd.

Mind you, the cops may have slapped a keylogger on your system ahead of time. If that's the case, you're screwed.

Lawyers and hackers, please rip my idea to pieces and tell me what you think...

You'd have to be careful about the choice of encryption algorithms when you do this. There are good reasons (which I can't cite off the top of my head; I'm no cryptographer) why triple DES, for example, has an encrypt-decrypt-encrypt pattern, rather than encrypt-encrypt-encrypt. Even then, all you achieve is a doubling of the effective key length, not a tripling (and remember that the actual key is three times as long - each step uses a different key).

Cryptography is hard. I know enough to know that I know nothing about it, and that I'd screw the pooch on any crypto system I might implement. If you haven't a very solid maths background, and a lot of experience breaking cyphers (and I'm talking about more than just the simple Julius shift here), odds are extremely high that there's a flaw you've overlooked in your system.

Well there is a good reason why it's implemented as encrypt-decrypt-encrypt, but it's not for cryptographic strength. Instead this has its roots in the hardware backwards compatibility.That is to say that if you create an encrypt-decrypt-encrypt box and feed it the same key for all the crypto operations, you get plain DES encryption.(i.e. encrypt m with x = c, decrypt c with x = m, encrypt m with x = c). If you want proper 3 DES you just feed it different keys.So instead of having to create a box that does

To assert your Constitutional rights, you'll need ready access to $50K for lawyers (and perhaps expert witnesses); otherwise you'll get the Public Defender and it will be explained to you that your only option is to plead guilty, thereby avoiding being sentenced to 0xFF years in jail. IAAL.

You should use ROT-9 followed by ROT-8 followed by ROT-9 again. ROT-13 is pretty weak, but if you use different numbers, apply encryption multiple times, your data will be much safer. TripleROT (9,8,9) is a standard by which all other methods are measured. All without requiring some fancy scheme concocted by guys with foreign-sounding names. Would you trust your security to a foreigner? with a beard?Oh, and IIRC, withholding the password would be obstruction of justice (assuming they obtained a warrant

IAAL and no you can't. Try to be funny and what they'll do is grant you immunity for anything revealed in the password itself. Then they'll force you to reveal the password or sit in jail for contempt. Once you reveal the password they can decrypt the drive and use that data in court (even if it's the same as the password).

The real key here is that the 5th amendment protects you from testifying against yourself. Your "papers" are not considered testimony and not protected.

It seems to me that the best approach to this problem might be to have a password that self-destructs when it detects that someone is about to physically break into your system. This way, there is no password to give them and whoever it is that is trying to do this (whether it's the Man or bin Laden) there's simply no way for them to succeed. Just watch out for those false positives...

In that case isn't the best way just to not know the password ? Just use whatever comes from/dev/urandom at the time to

I am an NSF–funded researcher in computer security, focusing on electronic voting. Data privacy and confidentiality is very important to us, as you can imagine.

Your idea is quite terrible.

First, what do you mean by a file "without signature"? Take a zip archive as an example--even if you strip off the zip header, any forensicist worth his or her salt can figure out it's a zip archive, just because of the way the data is structured. Encrypted filesystems have structure, too. A data forensicist can recognize an encrypted container on the basis of its structure. (Some people have recommended to you TrueCrypt in hidden volume mode. This is bogus. I'll explain that if you want.)

Second, you appear to not understand how crypto works. Two layers are better than one, right? So double ROT13 encryption is stronger than single ROT13, right? You're running smack into a major, well-known area of crypto. A lot of ciphers do not composite themselves well. You are almost always better off just picking one algorithm with a strong keysize than a composition of multiple algorithms.

Third, how do you plan on managing all of your keys? Key management is a thorny enough problem in the best of times. By relying on multiple keys you're multiplying the problem immensely.

First, what do you mean by a file "without signature"? Take a zip archive as an example--even if you strip off the zip header, any forensicist worth his or her salt can figure out it's a zip archive, just because of the way the data is structured. Encrypted filesystems have structure, too. A data forensicist can recognize an encrypted container on the basis of its structure. (Some people have recommended to you TrueCrypt in hidden volume mode. This is bogus. I'll explain that if you want.)

Let's imagine that you've got a TrueCrypt container on your hard drive. The FBI gets a tip that you're involved in child porn. You get arrested. The DA has a jailhouse snitch who'll testify that you have kiddie porn. The DA has a forensicist who will testify that you've got an encrypted container on your disk drive. You don't want to be doing 10-to-25 in federal pound-me-in-the-ass prison, because you're a scrawny pimply-faced geek and you don't want to get married off to the biker with the most cigarettes. You tell the DA "... look, okay, here's the passphrase to my TrueCrypt container. See? There's just porn in there I was hiding from my wife! But everyone involved is over 18! Let me go! It's bogus!"

The DA just smiles at you and says... "I'd like to see the hidden container inside that TrueCrypt volume. My forensicist says oftentimes people do that with TrueCrypt."

You say "umm... there isn't a hidden container... there's nothing more there..."

The DA continues to smile. "Prove it to me."

You say "umm... I can't... that's exactly what TrueCrypt means when they say it's hidden... you can't prove it exists and you can't prove it doesn't exist..."

The DA rises from the table. "Say hi to your husband for me when you meet him."

Moral of the story: it is very, very important that you be able to prove the existence or nonexistence of your data.

Can you explain more of this please?

I don't know how to make it any simpler. If compositing encryption functions makes things harder to break, we'd expect two applications of ROT13 to be stronger than one application of ROT13. It doesn't work that way. And in an exactly similar way, two levels of AES may or may not be any better than a single layer of AES. Or one layer of Blowfish and one layer of 3DES. Or...

If you want to get more sophisticated than this, you need to take a collegiate math course focusing on group theory.

You don't have to. It's HIS job to prove it IS there (e.g., you have to be proven GUILTY in a court of law, not NOT guilty. A subtle but important distinction). He can't strongarm you into giving up the hidden volume, if it exists, and if it doesn't exist, he especially can't.

I was hoping you'd mention how the structured nature of the hidden volume is a dead giveaway. But you didn't say anything about that, leading me to think you don't believe it to be a pr

What I love about Slashdot armchair lawyers is their naive faith in the criminal justice system.

So you go to trial. So you're acquitted. But by the time you get acquitted, you're front page news in all the local newspapers. You're getting death threats. Your family is shunned. You get let go from your job because you're bringing too much controversy. Your life, not to put too fine a point on it, is fucked.

Hatfill has never been charged. Jewell was totally exonerated, as was De Lorean. Wen Ho Lee pleaded guilty to a minor count just to make the madness stop, and received a profuse apology from the bench for how he was mistreated.

Our justice system is run by elected officials (with media support). If you want fair treatment (justice) you had better hope that:

- it's not an election year- the case has not generated a lot of media attention- the case is not worthy of media attention when the DA holds a press conference- the DA (and many others in the justice system) are not career building, and looking at your case as an opportunity to advance

The last one is the kicker. For every case there are dozens of people in the justice system that will get beneficial career advancement material from a successful conviction. That's my observation.

But the law and the legal system *did* work in these cases; it was society, the media etc. that didn't. Not that it helps the victims, of course, but you need to recognise that this is a failure of society, not one of the criminal justice system, if you want to fix it.

So you go to trial. So you're acquitted. But by the time you get acquitted, you're front page news in all the local newspapers. You're getting death threats. Your family is shunned. You get let go from your job because you're bringing too much controversy. Your life, not to put too fine a point on it, is fucked.

And what does this have to do with hidden containers? Your life is fucked at the point that you are initially questioned or arrested. If the cops are going to be so underhanded as to pursue a convi

The "flaw" pointed out by the GP is only a flaw if you're being tried in a kangaroo court. I don't think our court system has gotten that bad.

I mean, if you're dealing with a corrupt court where you're guilty until proven innocent, you don't even have to be using encryption to get screwed this way. The DA might just as well accuse you of using steganography to hide illegal photos in random files spread all across your hard drive, which is equally impossible to disprove.

I'm not sure what you mean by the "structured nature of the hidden volume", though. TrueCrypt hidden volumes have no plaintext header, just like main volumes, and as long as the crypto methods in use are good ones, the encrypted data will be indistinguishable from random bytes, no matter how well-structured the plaintext is.

There are attacks against hidden volumes, but they basically involve taking snapshots of the whole volume at separate points in time, then obtaining the main volume's key and checking whether any changes have been made to "unused" areas of the filesystem.

That is, I could sneak into your house and copy the disk today (version A), then come back next month, seize the disk (version B), and force you to give up the main volume key. I can then mount both versions of the partition and look for differences between them. If there are any areas that contained random data in version A, and different-but-still-random data in version B, I can be pretty sure it means you were writing to a hidden partition located there.

I think the best defense against that attack would be for TrueCrypt to randomly write chunks of new random data to the free space of mounted volumes, which would disguise the writes made to hidden volumes. (Of course you'd need to use both keys when mounting the main volume so it knew not to clobber your hidden data.)

You'd have a fairly strong defense against that accusation if your hard drive contains no steganography tools. That's sort of the the issue with truecrypt - it doesn't prove you have child porn, or even a hidden volume, but its not unreasonable to suppose you might, if you have truecrypt, there is other circumstantial evidence, and a 'snitch' whose just reliable enough of a witness to sway a jury.

Luckily, in a criminal case, the standard is "guilty beyond a reasonable doubt", not "one could reasonably suppose you might be guilty".

You know nothing about the legal system. In our court system, you are innocent until proven guilty, the burden of proof is on the state. So you don't have to prove there isn't a hidden volume, they have to prove there is. Given that there seems to be no way to do this, they can't make their case. You can't speculate that something might be there. That's one of the most fundamental objections they teach lawyers "Objection, speculation." So all they have is that you have a volume of legal porn, and someone of

In our court system, you are innocent until proven guilty, the burden of proof is on the state.

This is true for sufficiently high values of w, where w is your net worth. If you can't afford tens of thousands of dollars to fight a bogus charge, then you're effectively screwed, particularly if the charge is one of the very emotionally charged ones (child porn, rape, terrorism, etc.).

You'd quickly end up in a situation where you'd be facing a team of prosecutors, working with virtually unlimited taxpayer funds (gotta protect the children, right?), against your fresh-out-of-lawschool public defender, whom if you're unlucky, you might have to share with half a dozen other defendants. And chances are, they're going to believe you're guilty and (consciously or not) treat you like it.

There have been a lot of sociological studies and research done on the U.S. legal system. People who can't afford lawyers plead guilty at an astoundingly high rate, and the entire system is set up to "process" them as quickly as possible, from arrest through to prison.

The system works like you describe in the best case scenario, but even then, it'll probably leave you bankrupt.

I don't know how to make it any simpler. If compositing encryption functions makes things harder to break, we'd expect two applications of ROT13 to be stronger than one application of ROT13.

It is a cryptanalysis problem. Encryption scheme are designed so that your clear text will become close-to-random garbage when encrypted. Why? Because if it is not random, forensics can do statistical analysis on the crypted data 1/ to identify the encryption algorithm, 2/ to try to guess the encryption key (http://en.wikipedia.org/wiki/Cryptanalysis/ [wikipedia.org] for more details).

If you crypt your text twice (or more) you modify the entropy of the encryption scheme, and the encrypted data will be not optimally close to random data. As a conclusion, encrypting twice made your data less robust to forensics.

Please provide some links for this; it sounds deeply wrong to me. How would re-encrypting the already encrypted plaintext allow you to observe data shifting, when the point of encryption is to obscure the relationship between the plaintext and the ciphertext?

Here is the wiki for Fourier Transformations [wikipedia.org]. The rough gist for our purpose is that when you composit elements (multiple encryption schema) you get a new schema with identifiable characteristics that can be reversed back to the original elements. IE F

That sounds almost plausible, but I still don't believe it. I've spent a year or two studying cryptanalysis. Fourier transforms on encrypted data have never featured in any modern cryptanalytic approaches I've heard of.The whole point of encryption is to minimise those statistical artifacts. By encrypting a ciphertext again, you are only applying more entropy to data that already appears quite random. If you don't already have any idea of the underlying plaintext, comparing one ciphertext with a re-encry

I'm not an NSA funded security researcher, but I'm also slightly less of an arrogant prick than "rjh". So to answer your question about layering encryption without getting into all the you're-not-even-worthy-to-be-asking-this-question crap, here's a brief layperson's answer:

Essentially your idea is not a bad one, it's just a bit naive -- there are non-obvious subtleties which must be considered in order to make the idea work as well as you hope.

One issue is that some encryption algorithms (called "groups") have the characteristic that when applied two consecutive times with different keys, the result is the same as if the algorithm was applied only once with some other third key. If this is the case for your favorite algorithm, then your plan adds no extra security compared to just encrypting once. And apparently it's not always easy to know whether this is the case for a complex algorithm, so you should assume the worst.

Another issue is that if your adversary can guess some plaintext (e.g. by assuming it contains.doc or.jpg headers) they can use a technique that trades off storage for computation and break your multiple encryption much faster than you would have thought.

One way to overcome these weaknesses is by applying your encryption in "EDE" (encrypt-decrypt-encrypt) mode, where you encrypt with one password, then "decrypt" with a second password (which is obviously not really decrypting but just making the scrambling that much more horrendous), and then encrypting again with a third password. Even this is not as secure as you might expect, but it's still pretty good.

The well-known security and crypto expert Bruce Schneier has a great book called "Applied Cryptography" (Wiley, 2nd edition 1996, ISBN 0-471-11709-9) which is accessible to average smart, interested, non-NSA-funded Slashdot readers without advanced math degrees. It even has a brief chapter (15) on this exact topic. (Schneier has other great books too.)

Despite his attitude, "rjh" is right in implying that our common sense is not trustworthy in the area of cryptography -- some of the world's smartest people devote their lives to this stuff and have come up with astonishing and often counterintuitive results. Smarter people than us have already studied this idea, which is basically a good one even though it has pitfalls. Don't let anyone make you make you feel stupid for having an idea or asking a good question.

Sure it does - 2DES ~= DES in terms of security, while 3DES is better. Naturally, this means that the 3 level encryption scheme is dependent on the actual algorithm and serves mainly as a method for frustrating forensics. Probably AES - block shuffle - AES (different key) would make for some fun, but that assumes that they just want to convict you of something. If they think you can get at the data and want it bad enough, they'll just work you for it.

The only thing i believe it is a good idea is that if you encrypt it only once, they can try the different standard algorithms via "trial and error" until they get some plain text. Whereas if you put a second layer of encryption, they might not know they got the right algorithm/password as they will at most get the random-like bytes produced by your first encryption layer.

Ok you've got me thinking... speaking of stored passwords, what if you've entered the passwords and they're still stored in RAM when the cops nab your machine?The problem here is if you do not store the passwords in RAM, you'll be asked for the password every time you, say, access a jpg file or delve into the webcache. That potentially means retyping in 3 passwords a million bajillion times. If you do store it in volatile RAM, you could leave open a narrow window of opportunity for the cops which becomes a

actually, that's a bit extreme, all you need to do is to heat it above the curie temperature (300-380 for Fe-Nd alloys) at this point the magnetic properties become completely dependent on the applied magnetic field, so as it cools down again, the only magnetization left is due to the earths magnetic field.
Below this temperature you need to apply a strong magnetic field to reverse *most* of the magnetization (thats how normal recording works).
As an added bonus if you do this in such a way as there are not dust contaminants (inductive heating of the platters in a vacuum) you still have a working drive.

I believe the parent poster was speaking in terms of removing the platter from the drive and heating it in some sort of induction heater [wikipedia.org]. This allows precise control of temperature and only directly heats conductive materials. Building one requires only some fairly simple electronics [richieburnett.co.uk] (scroll down for action shots).

At work the standard we gave our service vendor for destroying failed drives involved a drill press and epoxy. We're concerned about data thieves, not Three Letter Agencies.

For my personal drives at home, I just use a three pound hammer. A scraped, smashed and warped platter hitting the trash bin is effectively unreadable, and all I'm really concerned about is a bad guy finding bank account information. If someone official really wanted a working drive of mine, pajama-clad ninjas would probably come for it in the middle of the day while I was at work anyway.

When I suffered a bizarrely bad disk crash (i.e., it crashed in an odd way that was much more destructive, and made the data much harder to recover, than most crashes; I've forgotten most of the details, but I remember that) a few years ago, I took my disk to a recovery specialist that does, among other things, contract work for the FBI. I got a brief glimpse inside their clean room. They had disks that had been pounded with hammers, run over with trucks, immersed in salt water... you name it, these guys could get data off it.

Eh, I hate feeding trolls.
Hey, anonymous weaselnuts? Disk crash is a valid, and descriptive, term for a disk failure. The heads don't touch the disk -- this ain't your fscking vinyl record. If they touch, or *crash*, into the disk surface, bad things happen. It's a crash. Valid term. More correct would be head crash.
I've opened up a disk after the distinctive sound to see the beautiful half-millimeter deep groove in the surface of the platter and little strings of metal littering the inside. I've also sent disks that made the same distinctive sound to a data recovery service and gotten back data.

In my first job, we had a 250 MB rack mounted hard drive. In those days, a head crash was almost like a car crash in terms of violence and noise. These days, of course, head crashes are much less violent, but certainly still exist.

That drive you opened was old then eh?Most current drives are glass platters. I found this out when I had a batch of DeathStars go bad. IBM wanted the drives back for RMA, but we had company restricted secrete data on the disks... I informed IBM of the dilemma and that I would be drilling a pair of holes in the platters. When I did I heard a crunch sound, followed by broken shards of glass coming out the holes.Got replacement drives in no problem.-nB

Yeah, but at what point does recovering the data become prohibitively expensive?

At the point where the disk has been entirely overwritten *once* with data. In theory, someone with very specialised equipment could pick out the residual flux transitions from the new ones. However, modern (or rather, disks larger than tens of gigabytes) use a different modulation scheme similar to QAM, and once that is overwritten the old data is irretrievably gone.

I think you're making a big assumption there, I've worked for the government and with the police on several occasions... thus far I wouldn't consider most of them competent beyond a first year systems administrator, they have a lot of books that explain processes to them that were written by someone far more intelligent but often have to consult with someone who knows their shit to even complete the more difficult processes. If you do something that falls far outside their realm of commonly available and used encryption, knowledge, etc... you stand a fair chance of them not being able to break it *IF* you're not someone they consider a big fish. If you're someone they consider a big fish, they'll keep calling in bigger guns until they do get someone who can do whatever needs done to get into your data. Keep a nice sized tub of thermite on top of your pc that runs the full length with a magnesium strip in it and connect it to something that can ignite it... if you see them coming and can ignite it before they get to you, there won't be a pc and potentially a standing room by the time it finishes burning out... shy that, if they got undamaged physical hardware... they can get the data eventually if you're important enough.

Any hacker/script-kiddie with a working knowledge of touch and a 'find' command could wreak equal havoc. Combined with a quick filter and another perl script to generate random timestamps, all launched regularly from cron? Forget it. Forensics folks would be better off scouring logs for a non-tainted timestamp and counting directory inode entries for approximate age.

Of course, this says nothing of rootkits, which can be downright subversive, embedding themselves into kernel space where not even the OS knows they exist, where they can wreak untold havoc with historical system data or encryption. I bet there's even a script-kiddie version of anti-forensics tools out there, where it just cron-obfuscates anything trackable. Logs, timestamps, frequent automated sweeps of shred over unallocated disk blocks, inode reordering, and so on.

Now that I think about it, that might be a good idea. I got some work to do.;)

Linux servers have become a favorite home for memory- resident rootkits because they're so reliable. Rebooting a computer resets its memory. When you don't have to reboot, you don't clear the memory out, so whatever is there stays there, undetected.

I don't mean to sound like a moron or naive but are Linux rootkits really that prevalent? After doing a quick google search for "rootkits for linux", I found a few for the old 2.0 and 2.2 Linux kernels... Have updates that have

I don't mean to sound like a moron or naive but are Linux rootkits really that prevalent?

Considering that rootkits originated in Unix (hence "root"), I imagine that they are as prevalent in Linux as they are in any operating system (the argument of uptime notwithstanding).

Besides, a rootkit does not have to reside in kernel space to be very effective. Simply replacing many of the key binaries (init, bash, getty, ls, top, ps, etc depending on *nix flavor) will do wonders for probably 98% of systems out there. That said, I'm sure there are some which do reside in kernel space (a kernel module perhaps?) or maybe even some that are simply modified kernels (the source is available after all). How do you know that the kernel your system is running has not been compromised?

After doing a quick google search for "rootkits for linux", I found a few for the old 2.0 and 2.2 Linux kernels...

I tend to doubt you'll find the latest and greatest rootkit via Google. If you know the right people, I'm sure you can get whatever you need.

Any hacker/script-kiddie with a working knowledge of touch and a 'find' command could wreak equal havoc. Combined with a quick filter and another perl script to generate random timestamps, all launched regularly from cron? Forget it. Forensics folks would be better off scouring logs for a non-tainted timestamp and counting directory inode entries for approximate age.

And that seems to be the point - how many of these types actually know how to use touch or find... much less put together a perl script? By "hobbiest" they're not talking about our level of knowledge... they're talking average punk who thinks double-clicking a rootkit is advanced hacking. Criminals aren't always the sharpest crayons in the box.

I met one of the FBI agents involved in the investigation of Zimmerman over PGP. After that case, she moved on to child pornography cases. I asked her how many times they ran in to PGP being used by people trading in kiddie porn. Not a single one. She noted that the folks they were busting just weren't smart enough to understand that kind of thing.

That basic precautions are showing up enough to give investigators a problem says something both about the attackers and the investigations.

I met one of the FBI agents involved in the investigation of Zimmerman over PGP. After that case, she moved on to child pornography cases. I asked her how many times they ran in to PGP being used by people trading in kiddie porn. Not a single one. She noted that the folks they were busting just weren't smart enough to understand that kind of thing.

<advocate client="Devil">So that means one of two things:1. Smart people aren't trading in child pornography or2. Smart people weren't caught to begin with, and still aren't

And it probably shows just how stillborn general encryption of mail is. If average people don't learn that under threats of years in prison, what could possibly make regular people do it?</advocate>

So that means one of two things:1. Smart people aren't trading in child pornography or2. Smart people weren't caught to begin with, and still aren't

Well - you've got to keep in mind the context of our discussion. We were going out to lunch and I'm not exactly sure how it started... but I was mentioning Zimmerman's woes over PGP and she said "oh yeah - I was one of the investigators on that one." We then talked a bit about the good and bad uses of PGP (she had always seen PGP as nefarious until coming to

The obvious message to law enforcement is that people don't like others going through their things.

Personally, I'm all for it! The timestomp tool they mentioned seemes more for oh-shit scramble-the-evidence rather than general usage... that kind of timestamp manipulation can really frig up a system.

Personally I'm a fan of disk encryption using algorythms and key-lengths that make it extremely impractical to get in once the system is powered down. If up however... you have three strikes at getting in and all future packets from your IP are silently dropped for several days. Local access isn't a problem either... open the case and power goes out... and after 10 minutes of idle-time the system locks (only way in is password or reboot... obviously reboot isn't helpful)

Call me paranoid. I am. I also like my privacy. Yes, I DO have something to hide: MY LIFE! I don't want you in my stuff at all!!! It doesn't matter that there is nothing illegitimate or illegal on the damn things, I still don't care.

Personally, I'm all for it! The timestomp tool they mentioned seemes more for oh-shit scramble-the-evidence rather than general usage... that kind of timestamp manipulation can really frig up a system.

I was thinking more in direction of "non-destructive fuckup of compromised machine", like say a machine you've trojaned. Make it hell to figure out how and what you've done. If you want to prevent forensic investigation on your own machine, encryption is much better than obfuscation.

I was thinking more in direction of "non-destructive fuckup of compromised machine", like say a machine you've trojaned. Make it hell to figure out how and what you've done. If you want to prevent forensic investigation on your own machine, encryption is much better than obfuscation.

Well lets see, Mr. Anderson has a huge encrypted file and his computer asks for his private key when it boots up vs. Mr. Anderson with a bunch of files with messed up timestamps. The formers says "I'm guilty" whereas the latter says "Poor me I got hacked.. and they put lots of bad stuff on my computer too!". Just because it's a jury of your peers doesn't mean they aren't incompetent boobs that will convict just because they feel like you probably did "something".

How hard can it be to make stuff, for all practical purposes, inaccessible? Truecrypt + VMplayer + keyfiles + good passphrases has to equal some pretty good security. Of course that only applies if they burst through the door, not if they came in quietly while you were shopping and installed keyloggers and screencap software ahead of time and then arrest you later. If they're that interested in you, and they have physical access to your system, you're toast anyway. But I somehow doubt the local PD is going to break a Truecrypt container or PGP key, unless your passphrase is written down...oh wait.

Powering off the machine (via the soft-power through mobo switch) triggers some action (lock-up next start, email/network/pager/phone alert, etc)

shutting down the power supply (using the switches on the power supplies) triggers some action (lock-up next start, email/network/pager/phone alert even with no power, etc)

physically unplugging all 3 power cords triggers some action (lock-up on next start, email/network/pager/phone alert, etc even with no power)

cutting the power to the location instantaneously triggers some action (lock-up on next start, email/network/pager/phone alert, etc)

and on many models, trying to remove the unplugged unit from a building triggers some action (email/network/pager/phone alert, etc) - with the appropriate RFID station in said building.

Parts of the machine stay on for a very long time without power, and the whole machine itself can take up to 30 seconds to power down with no power connected. The System Management board has it's own internal power (though minimal), and most every hardware or power related issue gets logged into the hardware's system log - even with no power to the machine (ie: pulling all plugs or hitting the circuit breaker will make the machine log a "No AC Power" with Time & Date stamp; and send out a notification - even though it has no AC power - before the machine drains what is stored internally).

Pretty neat piece of machinery - and at 130lbs and a ridiculously high "guaranteed uptime" I guess such functions arent much to expect. Even so, many far lower end Netfinity's and their Intellistation brethren have (had) at least a few of the same features/capabilities).

I am presuming the replacement i Series e-Servers do as well - though that is just a presumption, and reality may be far different.

-Robert

PS: Making a home brew solution is very easy [though I think some boards natively support this through their "Case Tamper" pins which just need to be wired to a case intrusion switch (standard roller arm switch)]

Hate to sound like a apple fanboi, but even for those with something to hide that don't know much about computers at all, and therefore lack the know-how required to use these tools, simply using Mac OS X and turning on File-Vault, sad as it sounds, is enough to confound the majority of law enforcement. Most of the contractors that the police in the UK use are windows only. I know for fact that any linux or 'specialist' computers get passed to a specialist data firm in Germany for decoding...Macs?Only in the most serious of cases are macs in the UK sent for hacking if File-Vault's on. They go to Canada and take upwards of a year to crack. If ever.Unless you've done something pretty fucking serious, and the police know the evidence is on the machine, just can't prove it, they usually won't go to the expense.Of course, only the most stupid and inept of morons would be doing illegal shit and storing it on their computer without using the most powerful encryption possible, and only storing that which absolutely must be stored. Mind you, criminals are not usually noted for their cunning and intelligence....

It goes without saying that the above does not translate to across the pond, nor does it apply on Security operations with terrorists and the like. How MI5 & MI6 do things is completely different and tends to involve some 'specialist' people from the likes of the I-corps and in-house solutions....I could elaborate, but I'm not THAT dumb.....

The one and only tool I've ever heard of them using is Encase. If Encase can't find it, it doesn't exist in their world. It does do OS-X though.

You are incorrect. I work as a software developer for a US company that specializes in computer forensic software and I work with investigators all over the world as well as the US. Encase definitely is the most widely used tool but it is most definitely not the only one, other tools similar to it are FTK (also widely popular) and something called iLook.

Let me let everyone in on a dirty little secret about 99% of police computer forensics experts... they are less skilled than most 9 year olds at recovering vital information. Many of them use bootable disks that just check the hard drive for IE's cached files and history, etc, etc. Simple stuff a child could do. These people aren't doing complex low level block analysis. They are doing the level of recovery parents do at the end of the night to see what websites their children went on. Does it surprise anyone then it's extremely easy to fool them? God forbid you use encryption, an OS they aren't familiar with, or hardware they've never seen. They'll never recover anything.

Don't underestimate the tools - many forensic experts couldn't find their way at all outside the tool, but the tools are rather good at three things:1) Point them to "interesting" catalogs on most operating systems2) Read pretty much any filesystem, including the odd Linux/BSD variants3) Scan for files (keywords, against a hash db etc.) without booting your OS

Encryption is the only thing that'll stand any serious investigation. Though I suppose it'll get you past the "should be bother to check his computer just in case" checks, there is plenty support for not "IE/Windows" machines.

Compound Document and File Analysis: Many files such as Microsoft Office documents, OutlookPSTs, TAR, GZ, thumbs.db and ZIP files store internal files and metadata that contain valuableinformation once exposed. EnCase automatically displays these internal files, file structures, data andmetadata. Once these files have been virtually mounted within EnCase, they can be searched, documentedand extracted in a number of different ways.

File Finder: This feature automatically searches through the page file, unallocated clusters, selected filesor an entire case, looking for predefined or custom file types. This feature differs from the standardsearch, because it looks through the defined areas for the file header information and sometimes thefooter.

Analysis: EnCase software has the ability to find, parse, analyze, display and document varioustypes of email formats, including Outlook PSTs/OSTs ('97-'03), Outlook® Express DBXs, LotusNotes NFS, webmail such as Hotmail, Netscape and Yahoo; UNIX mbox files like those used byMac OS X; Netscape; Firefox; UNIX email applications; and AOL 6, 7, 8, 9. In some cases,EnCase can recover deleted files and depending on the email format, the status of the machine.

Browser History Analysis: EnCase has powerful and selective search capabilities for Internetartifacts that can be done by device, browser type or user. EnCase can automatically parse,analyze and display various types of Internet and Windows history artifacts logged when websitesor file directories are accessed through supported browsers, including Internet Explorer, Mozilla,Opera and Safari.

My girlfriend told me that her nephew was going to college for "Computer Forensics" and my immediate response was, when he's done all he'll be able to do is catch cheating spouses. People who are engaging in real criminal activity are already using strong crypto and it's getting easier every day.

You just can't beat the numbers. If there is a 256 bit keyspace and a secure algorithm, you are not going to be able to crack the machine. I suppose that perhaps American and European law enforcement could take a page out of Israel's book and start using "strong persuasion" to get keys from suspects, but I don't imagine that happening any time soon.

That's what packages like TrueCrypt [truecrypt.org] with hidden volume support are good for. The Man tortures you, you give up a key, and he finds some fake secret files, while your real secret files are still safely hidden.

Don't knock it. Catching cheating spouses is a great way to get laid. You've already established that they've got no problem sleeping with people other than their husbands, which is 90% of the battle usually.

Robert Morris Sr. gave a talk long ago about the two major rules of crypto. First, never underestimate how far someone will go to read your data (for example, hiring Alan Turing and inventing digital computers). Second, look for plaintext, which will pop up in unexpected places while you perfect the algorithm that create the ciphertext.

If you typed a passphrase into a Windows machine, would you bet your freedom that the passphrase wouldn't show up in "strings/dev/hda", in a swap file, in an MRU list, or in the files of whatever spyware happened to infect that machine? Or that potentially incriminating file names wouldn't be tucked in the registry someplace?

Hiding things on a general purpose computer is still hard, despite the availability of little-known but powerful techniques like the ATA commands to create an unreadable Host Protected Area, or simply to misreport available disk space (I'm waiting for the hack that takes advantage of the fact that a disk drive has tens of megs reserved for its own use, several megs of RAM, and a 32-bit processor: a 1990s desktop worth of machinery that nobody thinks of as a computer).

Fearless prediction: technology will lose on both offense and defense. Successful police will flip accomplices, successful criminals will move to jurisdictions where they can form an under$tanding with the police, and anyone who tries to win a technological arms race will lose in the end.

I'm thinking even the most avante-garde anti-forensics tool could fool this guy. Yeah, anti-forensics might be a problem for him, but last time I checked, having a future date on your warez or kiddie porn won't save you from prosecution. In fact, using something like Timestomp is more or less likely to convince the jury that you are indeed a criminal.

And likewise, it takes a very *good* steganography tool to really hide things. Sure, you could fool your friends, but you aren't likely to fool a forensic investigator with a basic knowledge of statistics. Could I tell the difference between a good and mediocre steganography tool? Probably. Could the average criminal? Probably not. A mistake as simple as hiding your data in images gleaned from the web would be enough to trip someone up: Here's a hint - if the image looks the same as the one on the web, but the checksums don't match, something's up. I'm guessing a shell script could go through the hard drive and do most of the work for the investigator. 17 hours isn't so short anymore...

If you don't want the cops to find it, use encryption. If you want deniability, use the double-xor technique mentioned in Bruce Shneier's Applied Cryptography. But don't bother thinking that bogus timestamps are going to foil any serious forensic investigator. The relative location of a file's blocks on the hard drive is going to give at least an approximate date of file creation, even if you do obliterate the timestamp, and every forensic investigator worth his salt knows this.

Got a little something to hide? The point wasn't to provide deniability for your kiddie porn. The idea is more like, you rooted my machine, stole my data or did something evil with it, and now you want to cover your tracks. So you toast the logs as well as you can, you jumble up mtimes and permissions on files so that someone going back and doing forensics has a harder time establishing a pattern. The first step towards finding out who did something is figuring out when it was done, to find out who had access at that time, where to look in (non-compromised) logs, etc. So if you obscure that information you make it a little harder to trace things back to you. It's about hiding an identity, not data.

I read Ken Thompson's Reflections on Trusting Trust [acm.org], it has always occurred to me that any computer crime is completely untraceable. It is only laziness on the part of the criminal which allows him to get caught. It is possible for someone to completely cover their tracks and leave no evidence of their actions.

But it is also possible to log every action a hacker does. Erasing the logs doesn't do much when the compromised system is virtually hosted and every action recorded for later playback - on a system which isn't even visible to the hacker. And consider the possibility of tracing at the network level. It is possible to physically connect an ethernet chip to a network and capture all traffic on the network without ever joining the network. That is, the card can sniff the wire in a read-only mode without ever publishing its MAC address or responding to ARP queries. Even if the hacker does use encryption, can he really be sure that his machine hasn't been rooted and keylogged? Can today's hackers verify even the microcode inside their processors and BIOS? If he can cover his tracks, so can the FBI.

How does a hacker know his rootkit isn't spying on him? Even if you have the source, a compromised compiler or assembler can still produce a compromised executable. Should you verify the executable by hand, you still have the possibility of a vulnerability in the processor's microcode. Something as simple as making any area of memory available to the NIC when a certain opcode sequence is executed could be hidden very well and provide a veritable back door to law enforcement.

Unless you are willing to build your own computer from scratch and never connect it to a public network, you can never prove that you aren't compromised. Sure, we can talk statistics and likelihood and incentives and human factors and whatnot, but it doesn't change two fundamental aspects of the computer:

Changing computer data at the most basic level can be done without leaving any evidence, and

You can't prove the code you are running doesn't have security vulnerabilities without spending an inordinate and impractical amount of effort.

Your averge user - heck, even most programmers and hackers - don't have the time to trace through every possible instruction path in the software they use. They aren't going to burn their own BIOS EEPROMs to be sure the BIOS isn't bugging them. They aren't going to surgically remove the processor's cover and verify the die pattern to be sure the microcode isn't compromised.

Instead, they're going to trust the responses their computer shows them. Just like the rest of us - it's a gamble. Maybe the hacker compromised a bank - or maybe, the bank is in cahoots with the FBI, and he's just knocked over the honeypot. He won't know until he goes to the bank - and withdraws his cash, or gets arrested.

Even if the hacker does use encryption, can he really be sure that his machine hasn't been rooted and keylogged? Can today's hackers verify even the microcode inside their processors and BIOS? If he can cover his tracks, so can the FBI.

Yeah, if you assume Orwellian powers on the part of the FBI. No, the FBI doesn't have secret backdoors in all the hardware and software because it would take a VERY short period of time before those backdoors became public knowledge, making them near-useless AND compromising everyone's security. This is exactly what has happened in the past and I don't see them repeating these mistakes. I can't think of a worse idea than the FBI distributing troyjan rootkits into the wild.

Maybe the hacker compromised a bank - or maybe, the bank is in cahoots with the FBI, and he's just knocked over the honeypot. He won't know until he goes to the bank - and withdraws his cash, or gets arrested.

What would be interesting to me: a tool that deliberately modifies timestamps and/or creates ghost deleted files to tell a normal-looking story of computer use, when the actual history has been anything but.

In other words, forensics tools can assemble the history of file use on a disk. If it's known that the disk was in use before a certain date, but no timestamps can be found before that date (on current or deleted files), one may suspect the disk was wiped at that point. Likewise, physical disk usage for a given file system type has known and studied statistical characteristics over time. If the statistics are off, if you don't find deleted file images where you expect them, you may suspect that the freespace was wiped, or that certain unused disk space that would normally contain deleted file images contained files that are now wiped.

What happens when you have a tool that modifies timestamps on current and deleted files such that a normal distribution of them extend back before the date of disk wipe? Even worse, what happens if the tool can create "ghost" images of deleted files, in order to fool tools that look for normal statistical disk usage?

Once you have such a tool, wiping a disk and starting over can literally be done undetectably. So much for worry about having to maintain disk drive evidence after being hit with a subpoena.

By physically examining the disk you could better determine the age of the data -- but this is not how digital evidence is usually collected.In fact, this just exposes how ludicrous courts' treatment of digital "evidence" is. The information they accept as evidence can be trivially faked. Think it sounds far-fetched to be framed for a crime? That's not so difficult when someone can just flip a few bits on your hard drive, maybe via a memory-resident-only exploit, then call in an anonymous tip to the poli

The date a track was written could possibly be analyzed by looking at how it was written at the microscopic level, but this would probably destroy the disk itself. It would be very expensive. As far as I know, this is only theory and has not actually been done. If somebody has a technique, it would hope that it would require a lot of peer reviewed research to verify it's validity.
Anyway, the date a track was written may have nothing to do with the age of the data (file), as the OS may move files around for efficiency. This will not effect the timestamps of a file. The fact is that these timestamps are simply data written on the disk and can easily be changed.

As far as I know, there has not been one scrap of evidence showing that past disk writes can be examined through microscopy, or any other kind of direct physical examination.

The most powerful technique I know of would be Magnetic Force Microscopy (MFM), which is essentially a variant of AFM (Atomic Force Microscopy [veeco.com]) that uses a magnetized tip. When I was an undergraduate, I used AFM to image surface features as small as 50 nm, which a quick calculation shows to be comparable to the square root of the physical area used to store a bit on a modern hard drive. Presumably, somebody with more experience or better equipment could do better; it's not a difficult technique if you just want to learn the basics. To actually scan a hard drive in a reasonable amount of time would require a very specialized MFM machine, but I see no reason why such things wouldn't be available to various three-letter agencies.

Now, I don't know whether there is any residual information to get from an overwritten bit, but it would surprise me if there wasn't, and if there is, it can probably be gotten with MFM, if not an easier technique.

I'm going to approach this from the perspective of A Bad Guy, because realistically if you're not A Bad Guy and you get arrested you have already hit your security worse case scenario. You're now arrested, your computer is in government hands, and you are about to take major financial and reputational damage before being released. (Some folks might say I'm naiive for assuming you'll be released. Fine, don the tinfoil hats if it please you, but if The Man can lock you up when you haven't done anything the

It's usually quite possible, it depends generally on what you overwrite with, how you do it and how often you do it.Just filling the blanks with zeros, it's quite trivial to recover the data underneath. Filling it with random static makes it harder. Filling it 3 times makes it even harder. Filling it 30 times adds another layer of hardship.

Generally, though, you can assume this to be a lim 1/x function. It gets harder and harder to recover anything, to the point where you would really have to warrant the ex

No. For that matter, it's gone for good after one time. You don't even have to make sure all the most recent state transitions are the same direction (which would necessitate 2 passes unless all you're doing is EORing whatever's already there with 1; this is time-efficient, but also trivially reversible).

Once upon a time, heads didn't track so precisely as they do today, and there were sometimes minute traces of data either side of the track; and once upon a time, magnetic media had a wide hysteresis l